1. Field of the Invention
The present invention relates to a zoom lens barrel.
2. Description of the Related Art
In a known cylinder with a helicoid (helicoid cylinder) which constitutes a zoom lens barrel for a zoom compact camera or the like, a male helicoid is provided on an outer peripheral surface of a rear end of the cylinder in the optical axis direction. The portion of the cylinder in front of the male helicoid has a smooth cylindrical surface. Consequently, the front cylindrical portion is projected forward and exposed externally, in accordance with the feed operation by the helicoid. In such a helicoid cylinder, there is a possibility of the cylindrical portion exposed to the outside being damaged or deformed. Upon replacement of the exposed cylindrical portion, it is necessary to disassemble the mechanical portion as far as the helicoid, thus resulting in an inefficient repair operation. Moreover, the number of the elements that need to be replaced is uneconomically excessive.
It is an object of the present invention to provide a simple zoom lens barrel which can be easily disassembled.
To achieve the object mentioned above, according to an aspect of the present invention, a zoom lens barrel is provided, including a cylindrical member which is provided on the inner peripheral surface thereof with a female helicoid; a split helicoid cylinder including a rear helicoid ring portion which is provided on the outer peripheral surface thereof with a male helicoid which is screw-engaged with the female helicoid, and a front cylindrical portion separate from the rear helicoid ring portion, which is detachably connected to a front end of the rear helicoid ring portion in the optical axis direction so as not to relatively rotate, wherein the split helicoid cylinder is moved in the optical axis direction while being rotated; a linear movement cylinder which is disposed in the split helicoid cylinder so as to move in the optical axis direction; and a connecting structure for connecting the linear movement cylinder to the split helicoid cylinder so as to relatively rotate and so as not to relatively move in the optical axis direction, so that the rear helicoid ring portion and the front cylindrical portion of the split helicoid cylinder are maintained in a connected state by the connecting structure without being disconnected from one another in the optical axis direction.
In this zoom lens barrel, the helicoid cylinder can be split into the front cylindrical portion and the helicoid ring portion. The front cylindrical portion and the helicoid ring portion are integrally connected by attaching the linear movement cylinder thereto. Thus, the assembling and disassembling operations of the zoom lens barrel can be simplified.
According to another aspect of the present invention, a barrel assembly used in a zoom lens barrel is provided, including a cylindrical member which is provided on the inner peripheral surface thereof with a female helicoid; a split helicoid cylinder including a rear helicoid ring portion which is provided on the outer peripheral surface thereof with a male helicoid which is screw-engaged with the female helicoid, and a front cylindrical portion separate from the rear helicoid ring portion, which is detachably connected to a front end of the rear helicoid ring portion in the optical axis direction so as not to relatively rotate, the split helicoid cylinder being moved in the optical axis direction while being rotated; a linear movement cylinder which is disposed in the split helicoid cylinder so as to move in the optical axis direction; and a connecting structure for connecting the linear movement cylinder to the split helicoid cylinder so as to relatively rotate and so as not to relatively move in the optical axis direction, so that the rear helicoid ring portion and the front cylindrical portion of the split helicoid cylinder are maintained in a connected state by the connecting structure without being disconnected from one another in the optical axis direction.
Preferably, the connecting structure includes at least one circumferential groove centered about the optical axis provided on each inner peripheral surface of the front cylindrical portion and the rear helicoid ring portion, and a plurality of engagement pawls which are provided on the outer peripheral surface of the linear movement cylinder at different positions in the optical axis direction, wherein at least two engagement pawls of the plurality of engagement pawls include an engagement pawl which is engaged with the rear helicoid portion and an engagement pawl which is engaged with the front cylindrical portion. Each of the plurality of engagement pawls is engaged in each corresponding circumferential groove of the front cylindrical portion and the rear helicoid ring portion, respectively, so as to slide in the circumferential direction and so as not to relatively move in the optical axis direction.
Preferably, the engagement pawl which is engaged with the rear helicoid portion is located at a different position in the circumferential direction with respect to the engagement pawl which is engaged with the front cylindrical portion.
Preferably, the front cylindrical portion and the rear helicoid ring portion are provided on the inner peripheral surfaces thereof with pawl engagement/disengagement grooves which extend from the rear end of the rear helicoid ring portion to the frontmost circumferential groove of the front cylindrical portion in parallel with the optical axis when the front cylindrical portion is connected to the rear helicoid ring portion, so that the engagement pawls can be disengageably engaged in the circumferential grooves in the optical axis direction at a specific relative angular position between the split helicoid cylinder and the linear movement cylinder. Consequently, it is possible to engage or disengage only the front cylindrical portion in the optical axis direction at a specific angular position of the split helicoid cylinder, thus resulting in easy assembling and disassembling operations.
Preferably, each of the front end of the rear helicoid ring portion and the rear end of the front cylindrical portion is provided with one of a projection and a recess, and a corresponding other of the projection and the recess, wherein the projection and the recess engage with each other by a predetermined engagement length in the optical axis direction to restrict a relative rotation between the front cylindrical portion and the rear helicoid ring portion.
The present disclosure relates to subject matter contained in Japanese Patent Application No.11-305223 (filed on Oct. 27, 1999) which is expressly incorporated herein by reference in its entirety.